Distributor for pneumatically transported particle-form material



p 7, 1965 w. J. MATTHYS ETAL 3,204,942

DISTRIBUTOR FOR PNEUMATICALLY TRANSPORTED PARTICLE-FORM MATERIAL FiledFeb. 18, 1963 2 Sheets-Sheet 1 FIG.1

FIG. 4

v INVENTORS 48 John H. Kldwell BY William J. Marrhys ATTORNEY P 1965 w.J. MATTHYS ETAL 3,204,942

DISTRIBUTOR FOR PNEUMATIGALLY TRANSPORTED PARTICLE-FORM MATERIAL FiledFeb. 18, 1963 2 Sheets-Sheet 2 United States Patent 3,2il43 42DISTRIBUTOR FOR PNEUMATICALLY TRANS- PURTED PARTICLE-FORM MATERIALWilliam J. Matthys and John H. Kidwell, Alliance, Ohio,

assignors to The Babcock & Wilcox Company, New

York, rN.Y., a corporation of New Jersey Filed Feb. 18, 1963, Ser. No.259,199 7 Claims. (Cl. 266-28) This invention relates to a distributorfor pneumatically transported particle-form material and moreparticularly to a distributor wherein a mixture of carrier air andparticle-form fuel is divided into a plurality of effluent streams ofequal density and weight for introduction into and combustion in a blastfurnace.

Recent activities in the steel industry have been directed toward theadaptation of supplementary pulverized coal firing systems for use inblast furnaces. Experimental work indicates that it may be possible toreplace as much as 40% of the high cost coke used in blast furnaces withlower cost pulverized fuel, and to this end several schemes have beenproposed for preparing the pulverized fuel for introduction into theblast furnace. One of these schemes, in which the present invention maybe advantageously used, is shown and described in detail in US. PatentNo. 3,150,962, issued September 29, 1964. The economic justification forthe use of pulverized coal in blast furnaces, as well as the generalprerequisites of such a system, are fully described in theaforementioned US. patent and thus will not be repeated herein.-

Modern high capacity blast furnaces are provided with 16 to 24 air portsor tuyeres through which high temperature blast air, at about 1 800" F.,is introduced into the furnace above the hearth. Recent developments inblast furnace operating techniques have shown that the high blast airtemperatures result in improved conditions in the blast furnace hearthfor producing the desired quality of pig iron, and that operation atthese high temperatures will permit higher iron production rates thanhave heretofore been possible. To attain these high blast airtemperatures, an extensive program has been carried out to develop theregenerative stoves in which the blast air is heated. The high turnacetemperature associated with optimum furnace operation dictates that aminimum amount of relatively cool carrier air be introduced into thefurnace along with pulverized fuel. To avoid coking or burning of coalin the transmission lines, the temperature of the carrier air andpulverized fuel is limited by the characteristic coking or ignitiontemperature of the fuel being used. Thus it is desirable to use aminimum amount of the relatively cool carrier air to preclude dilutionof the high temperature blast air.

Another factor greatly aifecting blast furnace operation is theuniformity of combustion throughout the cross-sectional area of thehearth and both sections of the furnace. Any local upset in combustionconditions can cause severe channeling of the gases up through thefurnace stack or the formation of undesirable ash and slag ledgesimmediately above the combustion zone, either of which would seriouslyaffect the overall operation of the blast furnace. This requirement ofuniform combustion in the furnace dictates the necessity of using alarge number of blast air tuyeres and also makes it necessary todistribute the auxiliary pulverized coal as uniformly as possible withinthe combustion zone. This distribution of supplementary fuel can best beaccomplished by introducing equal amounts through all of the tuyeres.

From the above it can be seen that one of the primary problems in theadaptation of supplementary pulverized coal firing systems to blastfurnaces is that of equally distributing the'pulver'ized fuel to allofthetuye'res while using a minimum amount of relatively cool carrierair.

As described above, equal distribution of the coal is necessary tomaintain uniformity of reaction 'as it proceeds within the furnace,and-the minimum amount of carrier air is essential to avoid unduereduction in. the requisite hightenrperatur'e associated with blastfurnace operating conditions. During operation it may beinecessary,because of adverse conditions within the combustion zone of the furnace,to cut thejsupply of 'supp1e mentary fuel to one .or more of thetuyeres. During such times, it is obviously necessary that thefueldelivered to each of those tuyeres remainingin operation must bemaintained in substantially equal amounts so that a further unbalance infurnace conditions will not occur.

Therefore, the distribution system must be capable of adjustment inorder that equal amounts of fuel may be delivered to each and everytuyere which is kept'inservice to satisfy particular operatingconditions. Advantageously, the distributor herein disclosedaccomplishes this by a self-adjustment feature which isinhe'rent inthedesign.

-It is an object of this invention to provide a distributor for dividingan incoming-stream of pneumatically transported pulverized "fuelintoaplurality of efliu'ent streams having equal coal-air densities and coalquantities It is :a further object to accomplish this distribution andtransport with a mixture .of fuel and air having alow air/coal ratio,i.e. below 6 standard cubic feet of air per pound of fuel. A morespecific obg'e'ctof this invention is to provide a distributorifor usein conjunction with a suppleme'nta'ry pulverized fuel system for a blastfurnace whereby the 'fuel'rnay be equally distributed to a plurality oftuyeres and wherebyequable distribution 'to a lesser number of "tuyeresmay be similarly accomplished without having to make any changes to thedistributor.

To attain the above mentioned objects a distributor is provided whichincludes walls forming a vertically disposed, unobstructed chamber whichis symmetrical about its vertical axis. The chamber is closed at itsupper end or top, and a central inlet is provided in "thebottom thereof,through whichan air-fuel mixture to be distributed to multiple coalpipes is axially introduced into the chamber. A plurality of spacedoutlets, each .com- 'rnunicating with an associated coal. pipe, areprovided in the chamber walls forthe discharge of the mixture from thedistributor. These outle'tsa're arranged in a common horizontal planeand are equidistant from the vertical axis of the chamber. .;In such adistributor the density of the outgoing streams ofair and coal will'beequal, and if the outlets are of equal size, "the quantity of fuel goingto each outlebwil-La'lso be equal. When the distributor is used inconjnction with 'a'blast furnace, so .thateach outlet is connected toa'tn-yere by a conveying pipe or conduit, the flow from the distributorto each tuyere will be equal if the backpres'sureiof each outlet(pressure drop through each conduit system and its correspondingtuyere)is equal.

In addition, ,the present invention encompasses the method of operatinga seIni-direotpulverized fuel system in combination with a pressurizedblast.furnace whereby high pressure .conveying and drying air iscontinuously cycled through a pulverizer and separator, and pulverizedcoal is entrained in theair in'th'e former and separated from the air inthe latter. A minor portion of the conveying air is withdrawn'from. thecycle to be used for carrying the coal to the blast furnace, and anequal amount of heated makeup air introduced into the cycle. The carrier:a-iris'com-bined with a regulated quantity of pulverized coal from'thcseparator to form a mixture having an air/ fuel ratio of'less than 6standard cubic feet per pound of coal, and this mixture is divided intoa plurality of substantially equal density streams for delivery to eachof the tuyeres of the blast furnace.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawing and descriptivematter in which there is illustrated and described a preferredembodiment of the invention.

Of the drawings:

FIG. 1 is a sectional side view of a preferred embodiment of thedistributor;

FIG. 2 is a top view of the distributor shown in FIG. 1;

FIG. 3 is a schematic diagram of a blast furnace pulverized fuelpreparation and conveying system embodying distributors of the typeshown in FIGS. 1 and 2;

FIG. 4 is a schematic diagram showing in more detail that portion ofFIG. 3 which relates to the pulverized fuel distribution system and ablast furnace.

A preferred embodiment of the distributor is shown in FIGS. 1 and 2. Themain portion of the distributor is a vertically disposed rightcylindrical chamber formed by a tubular side wall 1 1, a top plate 12and a bottom plate 13. An inlet pipe is fitted into the central inletopening 14 in the bottom plate 13, and extends axially down-ward withrespect to the chamber 10. A plurality (five as shown in FIG. 2) ofequally sized outlet openings 16 are formed in spaced relation in a com-'mon horizontal plane in the side wall 11. The outlet pipes or conduits17 are fitted into these openings 16 and extend radially outward fromthe chamber 10.

In operation, a mixture of air and pulverized material is introducedaxially into the chamber 10through the inlet pipe 15. The mixture issubsequently discharged through the openings 16 in equal quantities andwith uniform densities in each of the pipes 17. As showndiagrammatically in FIG. 1, the jet effect of the incoming streampenetrates the full length of the chamber 10 and impinges on the topplate 12. The jet then mushrooms and a downward uniform recirculation ofthe mixture takes place with some of the mixture passing out of thechamber .10 through the openings 16. The portion of the mixture whichdoes not leave the chamber 10 continues downwardly to the bottom of thechamber 10, and forms, in an equilibrium condition, a reservoir ofmaterial that is re-entrained in the incoming stream.

Of particular significance is the fact that actual testing has shownthatthis distributor is capable of equally distributing air andpulverized solids mixtures having an extremely wide range ofair/material ratios, i.e., from above 12 to as low as 0.22 standardcubic feet of air per pound of pulverized material. Operation in thelower portion of this range would seem to suggest that the distributoroperation is somewhat akin to a fluidized bed; however, the principle ofoperation is not analogous to fluidized bed principles. In a fluidizedbed, the fluidized medium is introduced at low velocity over a wide areasuch that the entire body of material in a given zone is aerated.However, in this distributor, the confined inlet stream is introduced ata relatively high velocity into the enlarged chamber '10 to produce thejet effect described above. To further distinguish the principleinvolved from a fluidized bed, it should be noted that the distributoralso functions efiiciently at higher air/material ratios, i.e., above 12standard cubic feet of air per pound of pulverized material.

As a practical matter, a frusto-conical bottom (shown in phantom as 13'in FIG. 1) may be provided in the chamber 10 to avoid any accumulationin the bottom recesses of the chamber. As can be seen from the figure,this bottom has a downwardly diminishing diameter. Otherwise, therewould be a tendency for material to accumulate on the bottom plate 13adjacent the sidewall 11 which could result in intermittent slugging ofthe material through the outlets 16, or could produce a fire hazard.

Although the outlet openings 16 are shown in FIG. 2 as being evenlyspaced circumferentially about the side wall 11, it has been shown inthe tests to be hereinafter described that this uniform disposition ofoutlets 16 is not essential to satisfactory operation.

A distributor of the type shown in FIGS. 1 and 2 was tested usingmixtures of air and pulverized coal to determine its efiiciency as adistributor when operating under pressure. In these tests, air/ coalmixtures of known proportions were introduced into the distributorduring a measured period of time, and the quantity of material issuingfrom each of the outlet pipes 16 was collected, weighed and compared todetermine the degree of flow unbalance to the several pipes. From theseresults, the degree of unbalance (a measure of distribution efficiency)was determined as the difference between the highest and lowestpercentage of pulverized coal collected from the individual (pipes.-

The following are representative results obtained in tests on adistributor having a 4 inch pipe for the inlet 15, five 1 /2 inch outletpipes 17, and having a right cylindrical chamber 10 with an insidediameter of 15% inches and a height of 24 inches.

Table number one Test A B l C D I E F Distributor Press,

p.s.i.g 36. 5 37. 5 37. 0 36. 0 35. 3 35. 5 Total Coal, lb- 289. 0 532.5 759. 5 856. 0 782.0 009 0 Air/coal, s.c.f./lb l2. 6 7. 04 1. 38 0. 9050. 400 0. Percent collected Outlet:

21. 1 21.5 19.0 20. 5 20. 5 18.9 #2 19. l 19. 9 19. 4 20. 2 20. 2 20. 1#3 18. 7 18. 6 20. 2 l9. 2 l9. 5 18. 7 #4 20. 1 l9. 0 20. 9 19. 7 l0. 121. 5 #5 21. 0 21. 0 20. 5 20. 4 20.7 20.8 Degree of Unbalance. Percent2. 4 2. 9 1. 9 1 4O 1. 6 2. 8

Further tests, using the same distributor, were conducted with one, twoor three of the outlet conduits 17 closed off, and the resultingdistribution through the remaining conduits was equally as good as withall of them open and in use. Another series of tests showed that thequantity of coal flowing through each conduit 17 was directlyproportional to the air flow therethrough. This means that thedistributor provides a mixture of uniform density at the outlets 16, andthus it follows that when the resistance to flow through each ouletconduit 17 is equal, the quantity of coal flowing therethrough will alsobe equal.

In a series of tests, using a plastic model of the distributor describedabove, the diameter of the chamber 10 was varied to ascertain whetherany size limitations could be found. As a result of these tests, it wasdetermined that for satisfactory solids distribution the ratio of thechamber diameter to the diameter of the inlet 14 had to be maintainedbetween 3.5 and 8.0, and that optimum performance was obtained when thisratio was between 4.0 and 6.0. In the model tests, the flow pattern ofthe material within the distributor could be observed as bearing out theprinciples of operation discussed above.

In transporting coal at low air/ coal ratio such as have been described(below 6 standard cubic feet of air per pound of coal), further testinghas shown that the characteristic flow pattern is a fluctuating flow ora form of twophase flow commonly referred to as slugging, i.e.,separation of the two constituents into entities known as slugs. If thiscondition exists at the distributor inlet, it will be substantiallyeliminated when the mixture passes. through the distributor because ofinternal recirculation within the distributor chamber.

In the course of conducting the above tests and observations severallimitations in the design of the dis,

5. tributor' became apparent. To effect optimum perform ance, thedistributor must be vertically disposed, the outlets 16 must be in acommon horizontal plane and the inlet pipe 15 must be centrallypositioned in the bottom of chamber 10. Also the single inlet line 15-must be arranged to introduce the incoming stream axially into thechamber to assure uniform flow entering the distributor to produce thesymmetrical recirculation pattern described above. For best results, theinlet should have a straight vertical portion of about ten times itsinternal diameter.

The distributor shown in FIGS. 1 and 2 is the preferred embodimentbecause of its simplicity of construction; however, it may beconcludedthat variations in the design of the-distributor could be made withoutaffecting its performance or departing from the expounded principle ofoperation. For example, the outlet conduits 17 need not necessarilyextend radially outward from the chamber 10. Also, the chamber 10 doesnot have to be circular in cross-section but could, for example, behex-. agonal. or octagonal; however, in these instances it issuggestedthat the outlets 16 should be evenly displacedv It is alsocontem about the peripheryof the chamber. plated that the flat top plate12 could be replaced by one having a different shape. For example, ahemispherical or conical top could be used so long as the-characteristicflow pattern within the chamber is maintained. Generally speaking, thechamber 10 should at least be symmetrical about the vertical axis of thedistributor, and the outlets 16 should be equi-distant from thisvertical axis.

An auxiliary pulverized coal firing system for use in conjunction with ablast furnace and incorporating distributors of the type described aboveis shown in FIG. 3. The'blast'furnace 20 is of the usual type whereinprovisions are made for the delivery of iron ore, flux, and

coke through the upper end and for removal of slag and sor 21, and isheated to about 1800 F. by a battery of regenerative stoves 22. The hotblast air isdeliveredthrough duct 23 to a torus shaped bustle pipe 24which encircles the blast furnace 20 at about the level of the bosh.Theblast air is then introduced into the furnace.

20 through goosenecks 25 which extend through the air ports or tuyeres26. In this description, it will be assumed, for the sake of simplicity,that there-are l0 tuyeres 26 evenly spaced about the circumference ofthe blast furnace 20; however, it should be recognized that the presentinvention may also be used in conjunction with a blast furnace havingasmaller or greater number of tuyeres.

The raw coal to be fired in the blast furnace 20 is supplied to anatmospheric hopper 30, thence through a series of pressurized lockhoppers 31 having appropriate pressure-tight coal valves 32, and intothe puverizer 33. Conveying air for the prepared fuel is supplied to thepulverizer 33 from the recirculating fan34-through line 27.

The pulverized fuel, in suspension in the conveying air, is carried byline 35 to the'separator'36 where the coal/ air mixture is separated,the pulverized coaldropping into: the lower hopper 37 while the air isremoved at the top.

of the separator 36 through air line 38.- The majority of the separatedair is returned to therecirculatingfan 34 through line 40, the remainderbeing used as'carrier air for conveying pulverized coal from the lowerhopper 37 to the blast furnace 20 as will be hereinafter described.Make-up air for the conveyingair circuit is supplied from the compressor21 through lines 41 and the separatelyfired air heater 42. The make-upair for the conveying cycle is preheated to the desired temperature(about 400 F.) in the heater 42 and is introduced into the cycle throughthe mixingT 43. Thus theconveying air is.continuously circulated by thefan 34'through a cycle includ ing the pulverizer 33 andthe separator 36,andthe minor portion of the conveying air that is withdrawn from thecycle downstream of the separator 36 .for purposes of conveying thepulverized coal to the blast furnace 20. is

replaced by heatedair entering the cycle throughthe mix ing T 43.

The carrier air to be used for-conveying the pulverized.

coal from the lower hopper37 to the blast furnace 20, is

obtained from-air line 38-and..passed through carrier air. line 44 tothe mixing T 45. which is immediately-below: The carrier air flow isregulated the lower hopper 37; to a desired rate by valve 46' and theamount of pulverized coalflowing to the mixing T 45 is regulated bycontrol ofthe feeder 47 so that an air/ coal mixture of the.

desired density is cotninuously formed in the mixing T 45.

This air/coal mixture passes throughthe primary dis-.

each. Thus the air/ coal mixture is first divided into two streams intheprimary distributor 49, and each of. these streams is furthersubdivided into five streams each in the. two secondary distributors 51.Each ofthe outlet conduits 52 is arrangedto supply its air/fuel streamto a specific tuyere '26 of the blast furnace 20. In the drawing (FIG.3), for the sake of simplicity, onlyone outlet con-- duit 52is shown asbeing connected to its corresponding tuyere. From the above, it can beseen that distributors, of the typeherein described .could be arrangedto divide.

a mixture of air and pulverized coal-intopractically any desired numberof streams;

It should be noted that the pressure within the convey ing air cycleincluding the pulverizer 33 and the separator 36 is sufiiciently high toovercome, the cumulative static pressure within the blast furnace20 andthe pressure drop through the line 42, mixing T 45, distributor. inletline 48, distributor 49, outlet lines 50, distributors 51 andxconduits52. Thus, the pressurein the conveying air cycle is suficientlyhightopass the pulverized fuel from. the mixingT 45 through the entiredistribution system and into the blast furnace 20 without the aid of anybooster.

Although the distributor has been described herein in conjunction withthe preparation and conveying of air borne pulverized coal to a blastfurnace,.it should be recognized. that the disclosed distributor mayalso be used in conjunction with other systems for the distribution ofany pneumatically transported particle-form material.

In FIG. 4, the arrangement of the distribution system is shownschematically in relation to the blast furnace 20,

and the same reference numerals correspond to like parts in both FIG. 3and FIG. 4. As described before, the air/ coal mixtureenters via theprimary distributor sup? ply line 48 into the primary distributor 49,andis therein 1 dividedinto'two streams which pass by way of the two.secondary distributor supply lines 50, one supply line serving eachsecondary distributor51. Each of the secondary distributors 51 isconstructed with five outlet conduits 52 which conduct their respectivestreams of" air/coal mixture to a corresponding tuyere 26. Valves 53 arealso provided so that any of the conduits 52 can. be removed fromservice for maintenance as well as to compensate for'upsets inconditions within the blast furnace 20.

It should be noted that to obtain equal distribution through all of theconduits 52,-.the pressure drop through.-

all of the conduit flow paths should be equal; therefore, the conduits52 should be arranged and constructed so that equal back pressures areobtained at all of the outlets 7 of the secondary distributors 51 whenthere is equal flow through the outlets. If necessary, flow restrictorsmay be placed in the lines 52 to effect equality of pressure droptherethrough.

Preferably each secondary distributor 51 supplies fuel to its nearesttuyere 26, rather than having the outlet conduits or pipes 52, from theseveral secondary distributors 51, in a complicated, staggeredarrangement about the blast furnace. The arrangement shown allows thefuel distribution system to be designed and installed using a minimumamount of piping (conduits 52), and is possible only because of theunique operating characteristics of the distributors 49 and 51.

As previously mentioned, the quantity of fuel leaving each outlet of adistributor is directly proportional to the air flow through thatoutlet. To illustrate the operation of this distribution system, let usassume that the total coal flow to the primary distributor 49 is 9000pounds of coal per hour. With all ten of the cut-off valves 53 open,this will result in a flow to each tuyere 26 of 900 pounds of coal perhour. Let us now assume that one of the valves 53 is closed because of alocal operational upset Within the blast furnace 20, and that it isdesired to maintain the total coal input rate of 9000 pounds per hour.The air flow to the secondary distributor 51 will now be reapportionedto equalize the pressure at the outlets of the primary distributor 49 sothat the air flow to the secondary distributor 51 having all of itsassociated valves 53 open, will receive a larger portion of the air thanwill the other secondary distributor 51 which is now serving only fourtuyeres. Since the primary distributor 40 distributes the coal on adensity basis, a correspondingly larger portion of coal will also bedelivered to the secondary distributor having all valves 53 open. Thusthe quantities of coal flowing through all of the conduits 52 thatremain open will still be substantially equal, i.e., now about 1000pounds of coal per huor. From this description, it can be seen that theunique operating characteristics of the distributor provide equalquantities of coal to the tuyeres 26 that are retained in service evenwhen one or several of them are not being used. Thus the distributionsystem affords a large degree of flexibility to the supplementary coalfiring system so that it may be ct fectively utilized withoutinterruption even during periods when conditions within the blastfurnace 20 are upset.

While in accordance with the provisions of the statutes there isillustrated and described herein a specific embodiment of the invention,those skilled in the art will understood that changes may be made in theform of the invention covered by the claims, and that certain featuresof the invention may sometimes be used to advantage without acorresponding use of the other features.

What is claimed is:

1. Apparatus for distributing pneumatically transported particle-formmaterial comprising walls defining an unobstructed chamber formedsymmetrically about its vertically disposed axis and having its upperend closed, a bottom closure for said chamber including means forming acentrally disposed unobstructed inlet for the axial introduction intosaid chamber of a mixture of gas and particle-form material, said inlethaving a cross-sectional area substantially less than the horizontalcross-sectional area of said chamber, and means forming a plurality ofspaced outlets opening into said chamber, said outlets being arrangedequi-distant from said axis in a common horizontal plane displaced asubstantial distance from said upper end so that at least a substantialportion of the mixture entering said chamber impinges on said upper endand recirculates downwardly prior to exiting said chamber through saidoutlets.

2. Apparatus for distributing pneumatically transported pulverized fuelin a plurality of streams having substantially equal densitiescomprising walls defining an unobstructed chamber of circular horizontalcross section formed symmetrically about its vertical axis, saidchamchamber including a substantially cylindrical portion closed at itsupper end, a bottom closure of downwardly diminishing diameter beingformed with a centrally disposed unobstructed inlet for the axialintroduction into said chamber of a mixture of air and pulverized fuel,and means forming a plurality of circumferentially spaced outletsopening into said chamber, said outlets being a ranged equi-distant fromsaid axis in a common horizontal plane displaced a substantial distancefrom said upper end so that at least a substantial portion of themixture entering said chamber impinges on said upper end andrecirculates downwardly prior to exiting said chamber through saidoutlets.

3. In combination, a pressurized blast furnace of generally circularcross section and having a plurality of circumferentially spaced tuyerespositioned in a common plane in the lower portion thereof, said blastfurnace being of the type wherein it is desirable to introducepulverized fuel with a minimum amount of carrier air to all of saidtuyeres, and a semi-direct pulverized fuel system including independentsources of pulverized fuel and carrier air, means for continuouslycombining regulated quantities of said pulverized fuel and said carrierair to form a mixture for introduction into said blast furnace, adistribution systemfor dividing said mixture into a plurality of streamshaving substantially equal densities and being equal in number to thenumber of said tuyeres, and a plurality of conduits extending from saiddistribution system to said tuyeres for passing each of said streams toa corresponding one of said tuyeres, the quantity of pulverized fuelflowing in each of said streams being proportional to the combinedpressure drop through its corresponding conduit and tuyere, saiddistribution system including at least one distributor comprising wallsdefining an unobstructed chamber formed symmetrically about itsvertically disposed axis and having its upper end closed, a bottomclosure for said chamber including means forming a centrally disposedinlet for the introduction of a mixture of air and pulverized fuel intosaid chamber, said inlet having a cross-sectional area substantiallyless than the horizontal cross-sectional area of said chamber, and meansforming a plurality of spaced outlets opening into said chamber, saidoutlets being arranged in a common horizontal plane and beingequidistant from said axis.

4. In combination, a pressurized blast furnace of generally circularcross section and having a plurality of circumferentially spaced tuyerespositioned in a common plane in the lower portion thereof, said blastfurnace being of the type wherein it is desirable to introducepulverized fuel with a minimum amount of carrier air to all of saidtuyeres, and a semi-direct pulverized fuel systern including independentsources of pulverized fuel and carrier air, means for continuouslycombining regulated quantities of said pulverized fuel and said carrierair to form a mixture for introduction into said blast furnace, adistribution system for dividing said mixture into a plurality ofstreams having substantially equal quantities of said pulverized fueland being equal in number to the number of said tuyeres, and a pluralityof conduits having substantially equal pressure drops and extending fromsaid distribution system to said tuyeres for passing each of saidstreams to a corresponding one of said tuyeres, said distribution systemincluding at least one distributor comprising walls defining anunobstructed chamber formed symmetrically about its vertically disposedaxis and having its upper end closed, a bottom closure for said chamberincluding means forming a centrally disposed inlet for the introductionof a mixture of air and pulverized fuel into said chamber, said inlethaving a cross-sectional area substantially less than the horizontalcross-sectional area of said chamber, and means forming a plurality ofspaced outlets opening into said chamber, said outlets being equal insize and arranged in a common horizontal plane and equidistant from saidaxis.

5. In combination, a pressurized blast furnace of generally circularcross section and having a plurality of circumferentially spaced tuyerespositioned in a common plane in the lower portion thereof, said blastfurnace being of the type wherein it is desirable to introducepulverized fuel with a minimum amount of carrier air to all of saidtuyeres, and a semi-direct pulverized fuel system including independentsources of pulverized fuel and carrier air, means for continuouslycombining regulated quantities of said pulverized fuel and said carrierair to form a mixture for introduction into said blast furnace, adistribution system for dividing and mixture into a plurality of streamshaving substantially equal densities and quantities of said pulverizedfuel, said streams being equal in number to the number of said tuyeres,and a plurality of conduits having equal pressure drops and extendingfrom said distribution system to said tuyeres for passing each of saidstreams to a corresponding one of said tuyeres, said distribution systemincluding at least one distributor comprising walls defining anunobstructed chamber formed symmetrically about its vertically disposedaxis and having its upper end closed, a bottom closure for said chamberincluding means forming a centrally disposed inlet for the introductionof a mixture of air and pulverized fuel into said chamber, said inlethaving a cross-sectional area substantially less than the horizontalcross-sectional area of said chamber, and means forming a plurality ofspaced outlets opening into said chamber, said outlets being equal insize and arranged in a common horizontal plane and equidistant from saidarms.

6. In combination, a pressurized blast furnace having a plurality ofspaced tuyeres circumferentially arranged in the lower portion thereof,and a fuel feeding system for delivering pneumatically transportedparticle-form carbonaceous fuel to a plurality of said tuyeres, saidfuel feeding system comprising means for combining regulated quantitiesof said fuel and carrier gas to form a mixture for introduction intosaid blast furnace, a distribution system for dividing said mixture intoa plurality of streams having substantially equal densities, and aplurality of conduits extending from said distribution system to saidtuyeres for passing each of said streams to :a corresponding one of saidtuyeres, said distribution system including at least one distributorcomprising Walls defining an unobstructed chamber formed symmetricallyabout its vertically disposed axis and having its upper end closed, abottom closure for said chamber including means forming a centrallydisposed inlet for the introduction of said mixture axially into saidchamber, said inlet having a cross-sectional area substantially lessthan the horizontal cross-sectional area of said chamber, and meansforming 10 a plurality of spaced outlets opening into said chamber, saidoutlets being arranged in a common horizontal plane and beingequi-distant from said axis.

7. In combination, a pressurized blast furnace having a plurality ofspaced tuyeres circumferentially arranged in the lower portion thereof,said blast furnace being of the type wherein it is desirable tointroduce carbonaceous solid fuel with a minimum amount of carrier air,and a fuel feeding system for delivering pneumatically transportedparticle-form carbonaceous fuel to a plurality of said tuyeres, saidfuel feeding system comprising means for combining regulated quantitiesof said fuel and carrier air to form a mixture for introduction intosaid blast furnace, a distribution system for dividing said mixture intoa plurality of streams having substantially equal densities, and aplurality of conduits extending from said distribution system to saidtuyeres for passing each of said streams to a corresponding one of saidtuyeres, the quantity of solid fuel flowing in each of said streamsbeing proportional to the combined pressure drop through its respectiveconduit and tuyere, said distribution system including at least onedistributor comprising walls defining an unobstructed chamber formedsymmetrically about its vertically disposed axis and having its upperend closed, a bottom closure for said chamber including means forming acentrally disposed inlet for the introduction of at least a portion ofsaid mixture axially into said chamber, said inlet having across-sectional area substantially less than the horizontalcross-sectional area of said chamber, and means forming a plurality ofspaced outlets opening into said chamber, said outlets being arranged ina common horizontal plane and being equi-distant from said axis.

References Cited by the Examiner UNITED STATES PATENTS 1,741,184 12/29Denison 4886 1,841,664 1/32 Montal bano 22247'8 2,084,755 6/37 Young13756 1.1 2,292,897 8/42 Nielsen 2594 2,437,694 3/48 Hickman 259-42,650,161 8/53 Totzek -42 X 2,884,230 4/59 Pyle et al. 2594 3,150,9629/64 Pearson 7542 FOREIGN PATENTS 829,648 4/38 France.

1,137,147 1/57 France.

MORRIS O. WOLK, Primary Examiner.

JAMES H. TAYMAN, JR., Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,204,942 September 7, 1965 William J, Matthys er; a1,

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below- Column 1., line 55, for "both" read borsh column 4, inthe table, under column "A", line 2 thereof, for "289,0"

read 2980 column 7, line 5, strike out "cham";

column 9, line 12, for "and mixture" read said mixture -e Signed andsealed this 28th day of June 1966:

(SEAL) Attest:

EDWARD J. BRENNER ERNEST W. SWIDER Attesting Officer Commissioner ofPatents

3. IN COMBINATION, A PRESSURIZED BLAST FURNACE OF GENERALLY CIRCULAR CROSS SECTION AND HAVING A PLURALITY OF CIRCUMFERENTIALLY SPACED TUYERES POSITIONED IN A COMMON PLANE IN THE LOWER PORTION THEREOF, SAID BLAST FURNACE BEING OF THE TYPE WHEREIN IT IS DESIRABLE TO INTRODUCE PULVERIZED FUEL WITH A MINIMUM AMOUNT OF CARRIER AIR TO ALL OF SAID TUYERES, AND A SEMI-DIRECT PLUVERIZED FUEL SYSTEM INCLUDING INDEPENDENT SOURCES OF PULVERIZED FUEL AND CARRIER AIR, MEANS FOR CONTINUOUSLY COMBINING REGULATED QUANTITIES OF SAID PULVERSIZED FUEL AND SAID CARRIER AIR TO FORM A MIXTURE FOR INTRODUCTION INTO SAID BLAST FURNACE A DISTRIBUTION SYSTEM FOR DIVIDING SAID MIXTURE INTO A PLURALITY OF STREAMS HAVING SUBSTANTIALLY EQUL DENSITIES AND BEING EQUAL IN NUMBER TO THE NUMBER OF SAID TUYERES, AND A PLURALITY OF CONDUITS EXTENDING FROM SAID DISTRIBUTION SYSTEM TO SAID TUYERES FOR PASSING EACH OF SAID STREAMS TO A CORRESPONDING ONE OF SAID TUYERES, THE QUANTITY OF PULVERIZED FUEL FLOWING IN EACH OF SAID STREAMS BEING PROPORTIONAL TO THE COMBINED PRESSURE DROP THROUGH ITS CORRESPONDING CONDUIT AND TUYERE, SAID DISTRIBUTION SYSTEM INCLUDING AT LEAST ONE DISTRIBUTOR COMPRISING WALLS DEFINING AN UNOBSTRUCTED CHAMBER FORMED SYMMETRICALLY ABOUT ITS VERTICALLY DISPOSED AXIS AND HAVING ITS UPPER END CLOSED, A BOTTOM CLOSURE FOR SAID CHAMBER INCLUDING MEANS FORMING A CENTRALLY DISPOSED INLET FOR THE INTRODUCTION OF A MIXTURE OF AIR AND PULVERIZED FUEL INTO SAID CHAMBER, SAID INLET HAVING A CROSS-SECTIONAL AREA SUBSTANTIALLY LESS THAN THE HORIZONTAL CROSS-SECTIONAL AREA OF SAID CHAMBER, AND MEANS FORMING A PLURALITY OF SPACED OUTLETS OPENING INTO SAI CHAMBER, SAID OUTLETS BEING ARRANGED IN A COMMON HORIZONTAL PLANE AND BEING EQUI-DISTANT FROM SAID AXIS. 